Wide area communications systems, such as cellular telephone systems, operate at very high radio frequencies (RF). Such high frequency radio signals often are not capable of penetrating into buildings. As a consequence, radio devices that operate by connecting to external wide area networks will not work well, or may fail to work at all, when inside a building.
Radios that communicate with each other over short ranges in a building are susceptible to interference if they select operating frequencies which allow strong external transmitter signals to penetrate well into buildings. Radio devices that are capable of operating on multiple frequencies could potentially operate with improved performance if they select an appropriate operating frequency based on whether they are indoors or not and whether they want to connect to another device in a building or to an external, out of building device or network. However mobile radio devices do not have mechanisms to determine if they are in a building, and typically operate in the fixed manner whether indoors or outdoors.
Existing radio devices can detect a loss in signal. In some systems, that detection is then used to trigger a search for an alternate network or an alternate device to connect with. If an in-building system, such as a wireless local area network (WLAN), is available a device can potentially make use of that system. However, compatible WLAN systems are not available in every building and every location in a building.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.